Enhanced mechanism of scheduling request to multiple schedulers in a wireless network with multiple connectivity

ABSTRACT

Apparatus and method are provided to enhance scheduling request to multiple schedulers with inter base station carrier aggregation. In one novel aspect, the UE monitors and detects one or more SR triggering event. The UE selects one or more base stations based on predefined criteria and sends the SR to the selected one or more base stations. In one embodiment, at least one radio bearer of the UE is associated with multiple cell groups (CGs) in different base stations with association priorities. The association priorities may be configured by the network, derived based on predefined UE configurations, derived from load information received by the UE, or derived from radio measurements. In one novel aspect, the UE upon detecting SR failure triggered on a triggering radio bearer, sends SR failure indication to a RRC layer or associates the triggering radio bearer with a different base station.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part and claims priority under 35U.S.C. § 120 from nonprovisional U.S. patent application Ser. No.14/918,751, entitled “Enhanced Mechanism of Scheduling Request toMultiple Schedulers in a Wireless Network with Inter Base StationCarrier Aggregation,” filed on Oct. 21, 2015, the subject matter ofwhich is incorporated herein by reference. Application Ser. No.14/918,751 is filed under 35 U.S.C. § 111(a) and is based on and herebyclaims priority under 35 U.S.C. § 120 and § 365(c) from InternationalApplication No. PCT/CN2014/077179, with an international filing date ofMay 9, 2014, which in turn claims priority from Chinese Application No.201310172704.2, filed on May 10, 2013. This application claims thebenefit under 35 U.S.C. § 119 from Chinese Application No.201310172704.2. The disclosure of each of the foregoing documents isincorporated herein by reference.

TECHNICAL FIELD

The disclosed embodiments relate generally to wireless communicationsystems, and, more particularly, to enhanced mechanism of schedulingrequest to multiple schedulers in a wireless network with multipleschedulers.

BACKGROUND

A Long-Term Evolution (LTE) system offers high peak data rates, lowlatency, improved system capacity, and low operating cost resulting fromsimplified network architecture. LTE systems also provide seamlessintegration to older wireless network, such as GSM, CDMA and UniversalMobile Telecommunication System (UMTS). In LTE systems, an evolveduniversal terrestrial radio access network (E-UTRAN) includes aplurality of base stations, e.g., evolved Node-Bs (eNBs) communicatingwith a plurality of mobile stations referred as user equipments (UEs).

Scheduling Request (SR) is a request of scheduling radio resource foruplink (UL) transmission by the UE to the eNB. The SR informs the eNBthat the UE has new data to transmit. There are two types of SRtransmission: dedicated SR (D-SR), where the SR is conveyed on adedicated resource such as physical UL control channel (PUCCH), andrandom access-based SR (RA-SR), where the SR is conveyed on a contentionchannel such as random access channel (RACH).

Carrier aggregation (CA)/radio resource aggregation is introduced toimprove system throughput. With carrier aggregation, the LTE-Advancesystem can support higher data rate. Such technology is attractivebecause it allows operators to aggregate several smaller contiguous ornon-continuous component carriers (CCs) to provide a larger systembandwidth, and provides backward compatibility by allowing legacy usersto access the system by using one of the component carriers. LTE alsoallows carrier aggregation from different eNBs. Different from thetraditional wireless system, with inter-eNB or inter-RAT carrieraggregation, the UE needs to associate with multiple schedulers fromdifferent base stations. For inter-BS carrier aggregation, the basestations providing the carrier components are not physically collocated,it requires transmission medium and interfaces among the base stations.However, in a real deployed system, the exchanging of information amongbase stations is limited by the backhaul delay and additional overhead.Therefore, to increase the flexibility and efficiency in uplinkscheduling, the UE needs to be able to associate to individualschedulers in each base station. Each base station should have its ownprivate access channels for SR, channel station information (CSI), HARQfeedback and other functions to provide instantaneous assistant fordynamic scheduling. Accordingly, the UE should have additional functionsto handle communicating and coordinating with multiple schedulers fromdifferent base stations, which belong to the same or different RAT.

Improvements and enhancements are required for UE SR procedures tocommunicate and manage multiple schedulers from different base stations.

SUMMARY

Apparatus and method are provided to enhance scheduling request tomultiple schedulers in a wireless network with inter base stationcarrier aggregation. In one novel aspect, the UE monitors and detectsone or more SR triggering events. The UE selects one or more basestations based on predefined criteria and sends the SR to the selectedone or more base stations. In one embodiment, at least one LC of the UEis associated with multiple BSs with association priorities. In oneexample, the association priorities are configured by the network. Inanother example, the association priorities are derived based onpredefined UE configurations, or are derived from load informationreceived by the UE, or are derived from radio measurements.

In one novel aspect, the UE selects base station based on a predefinedselection algorithm. In one embodiment, the UE selection gives priorityto dedicated access channels over contention-based access channels. Inanother novel aspect, the UE performs logical channel prioritizationprocedure based on the association priorities. In yet another novelaspect, the UE cancels an SR to be sent to a selected base station upondetecting one or more conditions comprising: a buffer status report(BSR) being transmitted to another base station, and receiving an uplinkgrant that allows all data to be transmitted.

In one novel aspect, the UE monitors and detects SR triggering eventswith bearer-binding configuration. The UE upon detecting SR failure,sends SR failure indication to a RRC layer. In one embodiment, aftersending the SR failure indication to the RRC layer the UE generates anRRC message indicating a SR failure and sending the RRC message to aRadio Access Network. In one example, the UE after sending the SRfailure indication to the RRC layer associates the triggering LC with adifferent base station.

Other embodiments and advantages are described in the detaileddescription below. This summary does not purport to define theinvention. The invention is defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, where like numerals indicate like components,illustrate embodiments of the invention.

FIG. 1 illustrates a system diagram of a wireless network with inter-eNBcarrier aggregation or with inter-site radio resource aggregation, whichbelong to the same or different RAT in accordance with one novel aspect.

FIG. 2 is a schematic diagram of a network that supports inter-eNB orinter-RAT carrier aggregation with different types of cell groupsconfigured for a UE in accordance with embodiments of the currentinvention.

FIG. 3 is an exemplary flow diagram of sending the SR by the UEassociated with multiple schedulers in accordance with embodiments ofthe current invention.

FIG. 4 is a schematic diagram of a UE transmitting SRs to different basestations with bearer-binding configuration.

FIG. 5 is an exemplary flow diagram of SR for multiple schedulers withbearer-binding configuration in accordance with embodiments of theinvention.

FIG. 6 is an exemplary flow diagram illustrates applying an alternativeconfiguration after failure of SR attempts.

FIG. 7 is an exemplary flow diagram illustrates sending a problem reportto the RAN after failure of SR attempts.

FIG. 8 is an exemplary schematic diagram of a UE transmitting SRs todifferent base stations with soft-bearer-binding or no-bearer-bindingconfiguration.

FIG. 9 is an exemplary flow diagram of selecting a BS for SRtransmission for soft-bearer-binding or no-bearer-binding configurationbased on priorities of association.

FIG. 10 shows an exemplary flow diagram of selecting a BS for a UE withdifferent access channels configured.

FIG. 11 shows an exemplary flow diagram of PDU transmitting based on BSpriorities in accordance to embodiments of the current invention.

FIG. 12 is an exemplary flow diagram for selecting multiple BSs for SRsending in accordance with embodiments of the current invention.

FIG. 13 is an exemplary flow diagram for SR transmission with multipleschedulers by selecting one or more base station stations based onselection algorithms.

FIG. 14 is an exemplary flow diagram for SR transmission withbearer-binding configuration by performing enhanced adjustment based onSR failure indication.

DETAILED DESCRIPTION

Reference will now be made in detail to some embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings.

FIG. 1 illustrates a system diagram of a wireless network 100 withinter-eNB carrier aggregation or with inter-site radio resourceaggregation, which belong to the same or different RAT in accordancewith one novel aspect. Wireless network 100 comprises a main basestation eNB, also referred as an anchor eNB 102, two drift eNBs 103 and104 and a UE 101. Wireless network 100 supports multiple componentcarriers over different frequency channels, and carrier aggregation forserving cells originated from different eNBs. For uplink (UL)synchronization between a UE and its base station with respect to eachcomponent carrier (CC), the UE receives an UL timing advance from theeNB, which compensates for the propagation delay between the eNB and theUE. Since UE 101 can be served with radio resources from eNB 102, eNB103 and eNB 104, it may need to send SRs to one or more of the servingcells in wireless 100. Wireless network 100 can be an inter-RAT CCnetwork, with the anchor eNB 102 employs one technology, for example LTEor other cellular standards, while drift eNBs 103 and 104 usingdifferent wireless standards, such as Wifi. Regardless of the inter-BSCA is from the same standard or different standard, UE 101 is configuredto associate with different schedulers in each of the base stations, eNB102, eNB 103 and eNB 104. Upon detecting a SR triggering event, UE 101needs to first decides which base station the SR should be sent to.

In one exemplary configuration, wireless network 100 is a small cellnetwork. Initially, UE 101 camps on the macro cell served by eNB 102. UE101 establishes a Radio Resource Control (RRC) connection with the RadioAccess Network (RAN). eNB 102 provides and controls the initial RRCconnection and provides NAS mobility information and security input. eNB102 is the anchor eNB for UE 101. In a small cell network configuration,UE 101 moves within the coverage area of anchor eNB 102 while movinginto the coverage area of eNB 103. Upon entering eNB 103 coverage area,UE 101 can offload some traffic to eNB 103 if needed. In such situation,inter-eNB carrier aggregation can be configured for UE 101. UE 101 canuse additional resources from eNB 103, which is a drift eNB in the smallcell network system. The coordination between anchor eNB 102 and drifteNB 103 can be performed through Xn interface, for example, X3 or X2interface. The Xn interfaces, also known as backhaul connections providecommunication and coordination between eNBs. However, heavy reliance onsuch interface introduces undesirable delays for the system.

FIG. 1 also includes simplified block diagrams of protocol stacks insmall cell network 100 for anchor eNB 102, drift eNB 103 and UE 101. Atnetwork side, the protocol stack in anchor eNB 102 includes PHY, MAC,RLC, PDCP, RRC, and a scheduler. Because drift eNB 103 has its ownindependent scheduler, the protocol stack in eNB 103 includes at leastPHY, MAC, and a scheduler, and possible RLC too. At UE side, for UEsequipped with multiple PHY and MAC modules, they can be configured basedon its usage for carrier aggregation and small cell operation. In onenovel aspect of the current invention, UE 101 has multiple RLC layerswith corresponding MAC layers associated with corresponding PHY layer.In one embodiment, UE 101 is equipped with RLC1 corresponding to MAC1and established RRC connection with anchor eNB 102. As UE 101 moves intothe coverage area of eNB 103, the network may decide to aggregationresources from eNB 103 to offload traffics from UE 101. Therefore, UE101 is also configured with RLC2 corresponding to MAC2, and thecorresponding PHY sub-layer, which is PHY2.

FIG. 2 is a schematic diagram of a wireless network 200 that supportsinter-eNB carrier aggregation with different cell groups configured fora UE 201 in accordance with embodiments of the current invention. UE 201establishes RRC connection with anchor eNB 202. Network 200 supportsinter-eNB or inter-RAT carrier aggregation. UE 201 is configured withinter-eNB carrier aggregation. When UE 201 moves into the coverage areaof eNB 203, UE 201 can be configured with inter-eNB carrier aggregation.UE 201 can offload traffic from eNB 202 to eNB 203. UE 201 can beconfigured with multiple serving cells originated from two differenteNBs, for example eNB 202 and eNB 203. eNB 202 and eNB 203 can be a mixof different wireless standards as well. UE 201 can be configured tosupport inter-RAT carrier aggregation. For example, eNB 203 can be aNode B in a LTE network with the same radio access as eNB 202. Inanother embodiment, eNB 202 may be a 4G cellular node B while eNB 203 isa UMTS/3G celluar node B. In yet another embodiment, eNB 202 and eNB20 emay form a small cell network, where eNB 202 is a node B in a cellularnetwork, while eNB 203 may be a femto cell or pico cell supporting wifior other radio access standards. UE 201 is configured with multiple LCs,for example, LC #1 to LC #5. UE 201 is also configured with multiplelogical channel groups (LCGs). LC #1 is configured for UE 201 and isassociated with eNB 202. Similarly, LC #2 is associated with eNB 202,and LC #5 is associated with eNB 203. LC #3 is configured to be able toassociate with eNB 202 or eNB 203. Similarly, LC #5 is configured to beable to associated with eNB 202 and eNB 203. Multiple LCGs areconfigured for UE 201. LCG #1 contains LC #1, LC #2 and LC #3. LCG #2contains LC #4 and LC #5. Such configuration gives UE 201 largerbandwidth and more flexibility in aggregating resource but it poses aset of UL resource management issues. For example, upon detecting a SRtriggering event, the UE has to decide which eNB this SR should be sent.In the configurations like LC #1, LC #2 and LC #4 where the LC isassociated with one eNB, it is desirable to send the SR to thecorresponding eNB. For LCs that are associated with different eNBs, suchas LC #3 and LC #5, different algorithm is used to determine a basestation to send the SR.

FIG. 2 also includes a simplified block diagram of UE 201 in accordancewith novel aspects of the current invention. UE 201 comprises memory211, a processor 212, a transceiver 213 coupled to an antenna 218. UE201 also comprises various function modules including an SR detectionmodule 221, a configuration module 222, an association module 223, aselection module 224, an SR process module 225, a first MAC entity 226,a second MAC entity 227 and an SR failure control module 228.

SR detection module 221 monitors and detects SR triggering events.Configuration module 222 configures multiple LCs to one or more LCGs andfurther associates the LCs with one or more MAC entities. Associationmodule 223 associates a LC with one or more base stations based onpredefined criteria. In one embodiment, association module mayassociates a single LC with multiple base stations. Selection module 224selects a BS to send the SR based on predefined algorithms. First MACentity 226 communicates with a first base station. Second MAC entity 227communicates with a second base station. It is understood by one withordinary skills in the art that more than two MAC entities can beincluded in UE 201 when configured. With multiple MAC entities in UE201, UE 201 can associate with different schedulers residing indifferent base stations through the multiple MAC entities. SR failurecontrol module 228 detects SR attempts failures and takes action eitherto re-associate the LCs to a different BS or to send a RRC message tothe RAN indicating the SR failure event.

FIG. 3 is an exemplary flow diagram of sending the SR by the UEassociated with multiple schedulers in accordance with embodiments ofthe current invention. At step 301, the UE detects a SR triggeringevent. Because the UE is associated with multiple schedulers, the UEmust first decide which base station the SR should be sent to. At Step302, the UE selects one or more base stations to send the SR. Dependingon different configuration of the UE, the UE follows differentalgorithms in selecting the base station. At 303, the UE send the SR tothe selected base station(s).

As illustrated in FIG. 3, with inter-eNB and/or inter-RAT carrieraggregation, the UE may be associated with multiple base stationschedulers. There are two basic types of such association. The first oneis bearer-binding association. The second type is soft-bearer-binding orno-bearer-binding. Different embodiments are designed according to theconfiguration type of the UE.

FIG. 4 is a schematic diagram of a UE 401 transmitting SRs to differentbase stations with bearer-binding configuration. UE 401 communicateswith base station BS 402 and base station BS 403. UE 401 has multiplelogical channels (LC), LC#1 to LC#9, divided into a plurality of logicalchannel groups (LCG), LCG 411, 412, 413 and 414. Each LCG has one ormore LCs, or no LC. In bearer-binding configuration, each LC is onlyassociated with one BS. As an example shown in FIG. 1, LCG 411 has fourLCs, LC#1, LC#2, LC#3 and LC#4. LCG 412 has one LC, LC#5. LCG 413 hastwo LCs, LC#6 and LC#7. LCG #414 has two LCs, LC#8 and LC#9. Forbearer-binding configuration, each LCG has a corresponding buffer. LCG411 has LCG#1 buffer 421. LCG 412 has LCG#2 buffer 422. LCG 413 hasLCG#3 buffer 423. LCG 414 has LCG#1 buffer 424. Further, each LCG bufferhas a corresponding buffer status. LCG buffer 421 has LCG#1-bufferstatus 431. LCG buffer 422 has LCG#2-buffer status 432. LCG buffer 423has LCG#3-buffer status 433. LCG buffer 424 has LCG#4-buffer status 434.Each buffer status 431 to 434 is associated to only one MAC entity.Buffer status 431 and buffer status 432 are associated with MAC entity#1 441. Buffer status 433 and buffer status 434 are associated with MACentity #2 442. MAC entity 441 and MAC entity 442 include function entityfor SR processing. Each MAC entity has a corresponding physical layer.MAC entity 441 and MAC 442 have physical layer 451 and physical layer452, respectively. MAC entity 441 and MAC entity 442 are responsible forcommunication with BS 402 and BS 403, respectively. The associated LCsfor each MAC entity is also associated with the BS. The BSs 402 and 403perform resource allocation on the UE 401 for the associated LCs. Forexample, in FIG. 4, LC#1 to LC#5 are associated with BS 402, and LC#6 toLC#9 are associated with BS 403. Accordingly, the UE 401 can send SR tothe BSs 402 and 403 for UL radio resources.

UE 401 monitors and detects a SR trigger event. In one embodiment, whenUE 401 detects resources are needed for data transmission, it selectsone or more stations to send one or more SR requests. For bearer-bindingconfiguration, upon detecting one or more SR trigger events, UE 401determines for which triggering LCs, the SR triggers are. The triggeringLC is the LC for which the SR triggering events occurs. Since UE 401 isconfigured as bearer binding, each triggering LC corresponds to one BS,UE 401 selects the one or more corresponding BSs based on the triggeringLCs. If UE 401 detects the UL resource blocks (RBs) required areassociated to the same BS, UE 401 sends a SR to the same BS. Forexample, if UE 401 detects the required data transmission all relates toBS 402, at step 461, UE 401 sends a SR to BS 402. At step 462, BS 402responses with an UL grant. Similarly, if UE 401 detects the requireddata transmission all relates to BS 403, at step 463, UE 401 sends a SRto BS 403. At step 464, BS 403 responses with an UL grant. In anotherscenario, if UE 401 detects the UL RBs required are associated todifferent BSs, UE 401 sends SRs to the different BSs. For example, if UE401 detects that some RBs required are associated with BS 402 whileother RBs required are associated with BS 403, UE 401 sends SRs to bothBS 402 and BS 403.

FIG. 5 is an exemplary flow diagram of SR for multiple schedulers withbearer-binding configuration in accordance with embodiments of theinvention. At Step 501, the UE monitors buffer status of all the LCsconfigured. At step 502, the UE detects one or more SR triggeringevents. At step 503, the UE triggers a SR process. At step 504, the UEmanages all pending SRs. At step 505, the UE checks if the one or moreSR triggers are cancelled. At step 505 the UE determines whether the SRtriggers are cancelled, if yes, the UE goes to step 501 to monitorbuffer status of all configured LCs. If at step 505 the UE determinesthat not all SR triggers are cancelled, the UE moves to step 506. Atstep 506, the UE selects the associated BS based on the triggering LCsfor SR transmission. At step 507, the UE selects one or more cells fromthe selected BSs and sends the SRs. At step 508, the UE transmits bufferstatus report (BSR) and data to the selected BS.

For bearer-binding configurations, each LC configured in the UE arestatically associated with a base station. In one embodiment of thecurrent invention, the binding of a LC to a BS can be updated or changedbased on certain conditions. One condition is repeatedly failure of SRsto BS. It is possible that sending a SR on one of the selected BS failsafter repeated attempts. In one embodiment of the current invention, amethod of dealing with SR attempts failure on one of the selected BSscomprises indicating the SR attempts failure to RRC layer. Afterreceiving the indication, RRC layer applies an alternativeconfiguration. For example, the LCs originally associated to theselected BS are re-assigned to another BS. Then UE associates the LCswith another MAC entity, which is responsible for the communication tothe re-assigned BS. In another embodiment of the current invention, theRRC layer of the UE generates a RRC message indicating that there is aproblem with the communication to the selected BS and SR attempts to theBS failed. The message is sent from the UE to the radio access network(RAN). The two embodiments can apply to non-bearer-binding configurationas well. FIG. 6 and FIG. 7 illustrates exemplary flows for the twoembodiments.

FIG. 6 is an exemplary flow diagram illustrates applying an alternativeconfiguration after failure of SR attempts. At step 601, the UE performsSR attempts on the selected BS(s). At step 602, the UE determines if amaximum number of SR attempts has reached. The maximum number of SRattempts can be predefined or dynamically configured. If step 602determines that the maximum number of SR attempts has not reached, theUE moves back to step 601. If at step 602, the UE determines thatmaximum number of SR attempts has reached, it moves to step 603,otherwise go back to step 601. At step 603, the UE indicates to its RRClayer that SR attempts failed for one or more LCs. At step 604, the UEapplies alternative configuration based on the SR attempts failure. Atstep 605, the UE associates the LCs to another BS.

FIG. 7 is an exemplary flow diagram illustrates sending a problem reportto the RAN after failure of SR attempts. At step 701, the UE performs SRattempts on the selected BS. At step 702, the UE determines if a maximumnumber of SR attempts have reached. The maximum number of SR attemptscan be predefined or dynamically configured. If step 702 determines thatthe maximum number of SR attempts has not reached, the UE moves back tostep 701. If at step 702, the UE determines that maximum number of SRattempts has reached, it moves to step 703. At step 703, the UEindicates to its RRC layer that SR attempts failed for one or more LCs.At step 704, the UE generates a RRC message to indicate the SR attemptsfailure problem. At step 705, the UE sends the generated RRC message tothe RAN.

The second type of UE associating with multiple schedulers issoft-bearer-binding or no-bearer-binding. In soft-bearer-bindingconfiguration, a LC is configured to be associated with multiple BSswith different preference for different BSs. In no-bearer-bindingconfiguration, a LC is not bound to a BS but can be dynamicallyassociated with different BSs without any preference.

FIG. 8 is an exemplary schematic diagram of a UE transmitting SRs todifferent base stations with soft-bearer-binding or no-bearer-bindingconfiguration. A UE 801 communicates with a BS 802 and a BS 803. UE 801has multiple LCs, LC#0 to LC#9, divided into a plurality of LCGs, LCG811, LCG 812, LCG 813, and LCG 814. Each LCG has one or more LCs, or noLC, and corresponds to one or more than one buffers. For example, LCG811 has four LCs, LC#0, LC#1, LC#2 and LC#3. LCG 812 has one LC, LC#4.LCG 813 has two LCs, LC#5 and LC#6. LCG 814 has three LCs, LC#7, LC#8and LC#9. Each LCG has one or more corresponding LCG buffers. Forexample, LCG 811 has two LCG buffers, LCG#1 Buffer 821 for LC#0 andLC#1, and LCG#1 Buffer 822 for LC#2 and LC#3. LCG 812 has one LCGbuffer, LCG#2 Buffer 823 for LC#4. LCG 813 has one LCG buffer, LCG#3Buffer 824 for LC#5 and LC#6. LCG 814 has two LCG buffers, LCG#4 Buffer825 for LC#7, and LCG#4 Buffer 826 for LC#8 and LC#9. Each LCG buffer isassociated with a LCG buffer status. For example, LCG#1 Buffer 821 isassociated with LCG#1 buffer status 831. LCG#1 Buffer 822 is associatedwith LCG#1 buffer status 832. LCG#2 Buffer 823 is associated with LCG#2buffer status 833. LCG#3 Buffer 824 is associated with LCG#3 bufferstatus 834. LCG#4 Buffer 825 is associated with LCG#4 buffer status 835.LCG#4 Buffer 826 is associated with LCG#4 buffer status 836. Furthereach LCG buffer status is associated to only one MAC entity includingthe function entity for SR and BSR. For example, LCG#1 buffer status831, LCG#1 buffer status 832, LCG#2 buffer status 833 are eachassociated with MAC entity#1 841. LCG#3 buffer status 834, LCG#4 bufferstatus 835, LCG#4 buffer status 836 are each associated with MACentity#2 842. Each MAC entity has one corresponding physical layer thatcommunicates with a corresponding BS. For example, MAC entity#1 841 hasa physical layer 851, which communicates with BS 802. MAC entity#1 842has a physical layer 852, which communicates with BS 803. The associatedLCs for each MAC entity is also associated with the BS. BS 802 and BS803 perform resource allocation on the UE 801. Accordingly, the UE 801can send SR to BS 802 and BS 803 for UL radio resources.

When UE 801 is configured with soft-bearer-binding, a LC can beassociated with multiple BSs. If a LCG contains one or more LCs, forwhich a prioritized BS is configured for data transmission, each LC willcorrespond to one or more than one buffer. Each buffer is associated toa MAC entity corresponding to a BS. For example, LC#0, LC#1, LC#2 andLC#3 (corresponding to RB0, RB1, RB2 and RB3 respectively) belongs toLCG 811. LC#0 is configured to transmit only to BS 802, so LC#0 isassociated to BS 802. LC#1 is prioritized transmit through BS 803, soLC#1 is associated with BS 803. As illustrated, even though LC#0 to LC#3belong to the same LCG, LCG 811, they are associated with different BSs.Further, some LCs can associate with multiple BSs. For example, LC#4 maybe configured with no prioritized BS for data transmission. Therefore,LC#4 can associate with both BS 802 and BS 803 for SR transmission.Similarly, LC#5 to LC#8 may be configured with no prioritized BS fordata transmission. Therefore, upon detecting SR trigger for one or moreLCs of LC#5 to LC#8, UE 801 can transmit the one or more SRs to both BS802 and/or BS 803. Once one or more BSs are selected for transmittingthe SRs, UE 801 transmits SRs through corresponding MAC entities. Forexamples, at step 861, UE 801 transmits a SR to BS 802 through MACentity#1 841 via physical layer 851. At step 862, UE 801 receives an ULgrant from BS 802. Similarly, at step 863, UE 801 transmits a SR to BS803 through MAC entity#2 842 via physical layer 852. At step 864, UE 801receives a UL grant from BS 803.

For the offloading method of soft bearer binding, each RB has thepreference to which BS the SR and data shall be transmitted. Therefore,different radio bearers have different prioritized BSs for SRtransmission. It can also be configured whether the radio bearer can betransmitted through non-prioritized BSs. If the radio bearer is notallowed to transmit through the non-prioritized BSs, the SR and BSR forthe radio bearer can only be reported to the prioritized BS. Otherwise,the SR and BSR for the RB can be reported to the non-prioritized BSs. UEassociates each LC corresponding to each RB to one or multiple BSs andthe different multiple associations of a RB or LC have differentpriorities. For example, for each RB or LC, each BS is assigned adifferent priority e.g. BS₁>=BS₂>=BS_(3 . . .) >=BS_(n). The LCsassociated to one or multiple BSs also belong to a LCG according to theconfiguration. For the offloading method of no bearer binding, each RBhas no preference to which BS the SR and data shall be transmitted. SuchRB can be associated to both of the BSs.

FIG. 9 is an exemplary flow diagram of selecting a BS for SRtransmission for soft-bearer-binding or no-bearer-binding configurationbased on priorities of association. At step 901, the UE derives priorityof an association. At step 902, the UE selects the BS with the highestpriority for SR transmission. There are different ways to derive thepriority of an association.

In one embodiment of this invention, the UE receives the associationconfiguration from RAN through the RRC message. The UE associates eachLCs or RBs to one or multiple BSs based on the received configuration.So the association for each RB or LC is configured by RRC configuration.For example, the UE is configured with LC0 to LC6. The UE furtherreceives a RRC configuration from the RAN. The RRC configuration messageconfigures a BS1 is the prioritized BS for LC0 to LC3 and BS2 is theprioritized BS for LC4 to LC6. After receiving the RRC configurationmassage, the UE applies the configuration. The UE will associate LC0 toLC3 with BS1 and LC4 to LC6 with BS2 based on the configuration. The BS1and BS2 perform resource allocation for the associated RBs or LCs on theUE. Accordingly, the UE can send SR to BS1 for the associated LC0 to LC3and send SR to BS2 for the associated LC4 to LC6.

In another embodiment of the current invention, the priority of anassociation is derived from other configuration and may be based oncertain criterion implicitly. The BSs or the group of cells satisfyingthe criterion will have the highest priority. The criterion includes butnot limited to the following ones: a BS or group of cells that houses aCA primary cell, a BS with cells of the type femto cell or pico cell, aBS with cells on certain carrier frequencies. The priority of anassociation can also be derived from load information of the BSs. Forexample, the BS or the group of cells that have the lowest load has thehighest priority. The load information can be broadcasted through systeminformation (SI). After acquisition of the system information fromdifferent BSs, the UE compares the load among different BSs, and selectsthe BS with the lowest load.

In yet another embodiment of the current invention, the priority of anassociation can be derived from radio measurements. For example, a BS orgroup of cells that have the lowest pathloss to the UE will have thehighest priority. After measuring the pathloss of different BSs and thegroup of cells, UE compares the measurement results among different BSsand selects the BS with lowest pathloss.

The UE can send a SR through dedicated resources such as PUCCH orthrough contention based random access channel such as RACH.Accordingly, in selecting one or more BSs for the transmission of SR,the UE may select a BS based on the type of SR channel configured. Inone embodiment, the UE would first select the BS with dedicatedresources configured for SR. in other case, the UE selects the BSs withdedicated channel configured. The UE then derives the priority of theassociations with the selected BSs and selects the BSs one after anotherbased on the priority order for SR transmission until either the SRattempts on one of the selected BS succeed or the SR attempts on all theselected BSs fail. If the SR attempts through dedicated access channelson all the BSs failed, the UE would select the BSs with contentionaccess channel configured. The UE subsequently derives the priority ofthe associations with the selected contention-based BSs and selects theBSs one after another based on the priority order for SR transmissionuntil either the SR attempts on one of the selected BS succeed or the SRattempts on all the selected BSs fail.

FIG. 10 shows an exemplary flow diagram of selecting a BS for a UE withdifferent access channels configured. In one embodiment of the currentinvention, dedicated access channel takes precedence overcontention-based channels. The UE will use dedicated access channel forSR transmission first and then contention channels. For example, theprioritization for dedicated access channel among BSs is BS₁>=BS₂ andthe prioritization for contention access channels among BSs is BS₂>=BS₃.Upon detecting a SR triggering event, the UE first selects BS₁ becauseBS₁ has higher priority for dedicated channel. The UE transmits SRthrough the dedicated access channel associated with BS₁. Only when theattempts on dedicated channels with BS₁ and BS₂ all failed, the UEselects contentions-based channels. In selecting contention-basedchannels, the UE first selects BS₂ because BS₂ has higher priority forcontention-based channels. The UE subsequently to transmit SR throughthe contention channels associated with BS₃. So a lower priority accesschannel is used only if a number of unsuccessful attempts have beenperformed using the higher priority access channels. As shown in FIG.10, at step 1001, the UE finds the BSs with dedicated access channelconfigured. At step 1002, the UE derives the priority order of theassociation with the BSs configured with dedicated access channel. Atstep 1003, the UE selects the BSs with dedicated access channels basedon the priority order for SR transmission. At step 1004, the UEdetermines whether the SR attempts through dedicated channel failed forall BSs. If in step 1004 UE finds the SR attempt succeeded in one ormore BSs, the UE terminates the selecting procedure. If Step 1004 findsthat all SR attempts on all configured dedicated resources are failed,then the UE moves to step 1005. At step 1005, the UE finds the BSs withcontention-based access channel configured. At step 1006, the UE derivesthe priority order of the association with the contention-based BSs. Atstep 1007, the UE selects the BS based on the priority order for the SRtransmission. In one embodiment of the current invention, the UEdeclares radio link failure (RLF) upon all SR attempts failed on all theavailable contention-based channels.

The selecting of BS for SR transmission also applies to other ULtransmissions, including BSR and data transmissions. When multiplexingand assemble PDUs based on the UL grants received from a BS, theassociated LCs should have higher priority. The radio resources shouldbe allocated to the data available for transmission from the associatedLCs first. If after all available data are allocated, there are stillradio resources left, the pending data available for transmission fromnon-associated LCs will be served by the remaining UL grants. Suchnon-associated LCs are not restricted to be transmitted only to theprioritized BS. Therefore, if there is no UL shared channel (UL-SCH)resource available from the prioritized BS for a RB while UL-SCHresource is available from the non-prioritized BS, SR will betransmitted to the prioritized BS. BSR for the RB can be reported to thenon-prioritized BS and the pending data available for transmission forthe RB can be transmitted to the BS if there is any resource left.

In one embodiment of this invention, the method of multiplexing andassemble PDUs for data to be sent to a particular BS, compriseperforming logical channel prioritization (LCP) procedure on the LCs,which are associated to the particular BS or for which the associationwith the particular BS is the highest priority, checking whether anyradio resource left, and performing logical channel prioritizationprocedure on the LCs, which is not associated to the particular BS orfor which the association with the particular BS is a lower priority, ifthere is any radio resource left, and continuing performing LCP on LCsin association priority order for the association to the particular BSuntil data or resources ends One example of logical channelprioritization procedure in E-UTRAN system is described in the MACspecification 36.321.

FIG. 11 shows an exemplary flow diagram of PDU transmission based on BSpriorities in accordance to embodiments of the current invention. Atstep 1101, the UE receives UL grants from a particular BS. At step 1102,the UE performs LC prioritization on the associated LCs. Then UE choosesthe LC with the highest priority to use. At step 1103, the UE determinesif any radio resource left. If at step 1103, the UE determines thatthere is no more radio resource left, the UE terminates the procedure.If at step 1103, the UE determines that there are radio resources left,it moves to step 1104. At step 1104, the UE performs LCP onnon-association LCs or for which the association with the particular BSis a lower priority to chooses a suitable LC to use. At step 1105, theUE determines if there is any radio resource left. If at step 1105, theUE determines there is no radio resource left, the UE terminates theprocedure. If at step 1105 the UE determines that is resource left, theUE moves to step 1106. At step 1106, the UE determines if there any dataleft to be transmitted. If at step 1106 the UE determines that there isno more data left, the UE terminates the procedure. If at step 1106 theUE determines that there is data left, the UE moves to step 1107. Atstep 1107, the UE performs LCP on LCs in association priority order.

In one embodiment of the current invention, the UE can cancel a SRtrigger for the LCs associated with one BS based a predefined conditiondetected for a different BS. The predefined conditions include, a BSR istransmitted and a UL grant is received such that all pending data aretransmitted. For example, for SR transmitted through dedicated accesschannel, upon receiving UL grants from the selected BS, the UE instructsthe multiplexing and assembly procedure to generate PDUs, which containsBSR and SDUs from the associated RBs. The UE subsequently cancels thetriggered SR(s) if the PDUs includes a BSR which contains buffer statusup to (and including) the last event that triggered a BSR or when the ULgrants can accommodate all pending data available for transmission whichbelongs to the associated RBs. If the UL grants can accommodate allpending available for transmission, the SR triggered by the MAC entityfor other BS should also be cancelled.

When UE are configured to associate with multiple schedulers, the UE mayneed to determine a number BSs needed to transmit SRs based onpredefined criteria. In one embodiment of the current invention, thenumber of BSs needed is determines by either the required number of BSsfor SR transmission or the number of BSs having SR resources configured,whichever is less. The UE then selects the number of BSs for SRtransmission based on association priority. The UE can determine therequired number of BSs for SR transmission based on one or morecriteria. The first criterion is if the required number of BSs isconfigured by the RAN. The RAN configures a fixed number for BSselection through RRC signaling. The second criterion is if the buffereddata volume exceeds a predefined threshold. For example, the buffereddata volume is partitioned into different levels. Each level is mappedto a pre-defined number of BSs to which SR will be transmitted. Themapping relationship can be pre-configured or pre-defined in thespecification. Taking Table 1 for example, if the data amount is lessthan or equal to Threshold-1, only one BS will be selected for SR. Ifthe data amount is more than Threshold-1 and less than or equal toThreshold-2, two BSs will be selected for SR. If the data amount is morethan Threshold 2 and less than or equal to Threshold 4, three BSs willbe selected for SR. If the data amount is more than Threshold-3 and lessthan or equal to Threshold-4, four BSs will be selected for SR.

TABLE 1 Mapping relationship between the data amount and the number ofBSs Data Amount/Number of LCs having data Number available of BSs 0 <Data Amount <= 1 Threshold-1 Threshold-1 < 2 Data Amount <= Threshold-2Threshold-2 < 3 Data Amount <= Threshold-3 Threshold-3 < 4 Data Amount<= Threshold-4

The third criterion is if the data available for transmission is forcertain logical channel(s), multiple BSs will be selected. For example,for SRB for enhanced reliability, or for certain LC that is known torequire high data transmission performance. Same as criterion 2, thenumber of such RBs or LCs having data available for transmissiondetermines how many BSs will be selected. The fourth criterion is if thedata available for transmission is for SRB and is a particular message,multiple BSs will be selected. For example, the particular message is anespecially important message.

FIG. 12 is an exemplary flow diagram for selecting multiple BSs for SRsending in accordance with embodiments of the current invention. At step1201, the UE determines the required number of BSs to transmit the SRsbased on certain criterion. At step 1202, the UE determines an actualnumber of BSs by taking the minimum of the number of required BSs andthe number of BSs having resources configured. At step 1203, the UEselects the determined number of BSs for SR transmission base on thepriority.

FIG. 13 is an exemplary flow diagram for SR transmission with multipleschedulers by selecting one or more base station stations based onselection algorithms. At step 1301, the UE detects a scheduling request(SR) trigger event in a wireless network with carrier aggregation (CA),wherein the UE is configured with multiple logical channels (LCs) thatbelong to one or more logical channel groups (LCGs), and wherein atleast one LC is configured to associate to multiple base stations with tassociation priorities. At step 1302, the UE selects one or more basestations based on a selection algorithm. At step 1303, the UE transmitsone or more SRs to the selected one or more base stations.

FIG. 14 is an exemplary flow diagram for SR transmission withbearer-binding configuration by performing enhanced adjustment based onSR failure indication. At step 1401, the UE detects a SR triggered by aBSR in a wireless network with carrier aggregation (CA) associated withmultiple base stations, wherein the UE is configured with multiple LCsthat belong to one or more LCGs, and wherein a triggering DC, for whichthe BSR is triggered for, is associated with a base station or thetriggering LC is associated with a base station with highest priority.At step 1402, the UE transmits a SR to the base station associated withthe triggering LC. At step 1403, the UE detects an SR attempt failureevent. At step 1404, the UE sends an SR failure indication to a radioresource control (RRC) layer. At step 1405, the UE performs an enhancedadjustment based on the SR failure indication.

In addition to be applicable to LTE system, in one embodiment, theenhanced mechanism of scheduling request can also be applied to NewRadio (NR) radio access technologies and Multi-RAT Dual Connectivity(MR-DC) with multiple base station, e.g., one or more base stationsillustrated in FIG. 1 and FIG. 2. The anchor base station 102 can be amaster node MN and the drift base station 103 can be a secondary nodeSN. Each bases station has multiple cell groups which can be used toserve the UE.

E-UTRAN supports MR-DC via E-UTRA-NR Dual Connectivity (EN-DC), in whicha UE is connected to one eNB that acts as a MN and one en-gNB that actsas a SN. The eNB is connected to the EPC via the S1 interface and to theen-gNB via the X2 interface. The en-gNB might also be connected to theEPC via the S1-U interface and other en-gNBs via the X2-U interface.

NextGen RAN (NG-RAN) supports NG-RAN E-UTRA-NR Dual Connectivity(NGEN-DC), in which a UE is connected to one ng-eNB that acts as a MNand one gNB that acts as a SN. The ng-eNB is connected to the 5GC andthe gNB is connected to the ng-eNB via the Xn interface.

NG-RAN supports NR-E-UTRA Dual Connectivity (NE-DC), in which a UE isconnected to one gNB that acts as a MN and one ng-eNB that acts as a SN.The gNB is connected to 5GC and the ng-eNB is connected to the gNB viathe Xn interface.

As is known, according to radio interface protocols in LTE or NR, aradio bearer is used to transfer data and control between the UE andRadio Access Network (RAN). Radio bearers (RB) are for services providedby RLC/PDCP/BMC layer to higher layers. The RB may be classified into asignaling RB (SRB) for transferring RRC messages in the control planeand a data RB (DRB) for transferring user data in the user plane.Logical channels are used for services between the RLC sublayer and theMAC sublayer, and can be classified as either a control or trafficchannel.

In an alternative embodiment, the preceding embodiments using theterminology “logical channel (LC)” illustrated in FIG. 1 to FIG. 14 canalso be implemented using radio bearer. Correspondingly, one radiobearer may be associated with multiple cell groups (CGs) in differentbase stations.

In another embodiment, the soft-bearer-binding in the precedingembodiments may also be referred as split bearer, and theno-bearer-binding in the preceding embodiments may also be referred asmaster cell group (MCG) bearer/secondary cell group (SCG) bearer.

Although the present invention has been described in connection withcertain specific embodiments for instructional purposes, the presentinvention is not limited thereto. Accordingly, various modifications,adaptations, and combinations of various features of the describedembodiments can be practiced without departing from the scope of theinvention as set forth in the claims.

What is claimed is:
 1. A method comprising: detecting a schedulingrequest (SR) trigger event by a user equipment (UE) in a wirelessnetwork with a plurality of component carriers from multiple basestations, wherein the UE is configured with multiple radio bearers (RBs)that are associated to one or more logical channel groups (LCGs),wherein at least one RB with RLC bearers is configured to associate tomultiple cell groups (CGs) in different base stations; selecting one ormore base stations based on association priorities for the differentbase stations; and transmitting one or more SRs to the selected one ormore base stations.
 2. The method of claim 1, wherein the associationpriorities are configured by the wireless network via radio resourcecontrol (RRC) configuration.
 3. The method of claim 1, wherein theassociation priorities are derived based on predefined UEconfigurations, comprising: a base station or a CG that houses a PCellfor CA, a base station configured with femto or pico cells which havethe highest priority, and a base station with cells configured with apredefined carrier frequency.
 4. The method of claim 1, wherein theassociation priorities are derived from load information received by theUE.
 5. The method of claim 1, wherein the association priorities arederived from radio measurements.
 6. The method of claim 1, wherein theset of association priorities is specific to an access channel.
 7. Themethod of claim 6, further comprising: declaring Radio Link Failure(RLF) for the CG upon detecting access failures on the associated basestations and all available access channels of the associated basestation.
 8. The method of claim 7, further comprising: initiating RRCconnection re-establishment when RLF is declared for all base stations.9. The method of claim 6, wherein dedicated access channels are givenhigh priorities over contention based channels.
 10. The method of claim1, wherein more than one base stations are selected upon detecting oneor more conditions comprising: a volume of buffered data for one or moreRBs exceeding a predefined threshold, data available for transmission isfor a RB with high performance requirement or for a signaling radiobearer (SRB) for enhanced reliability, data available for transmissionis for SRB in a message, and a pathloss value is less than a predefinedvalue.
 11. The method of claim 1, further comprising: sending a bufferstatus report (BSR) to the selected one or more base stations.
 12. Themethod of claim 1, further comprising: performing a logical channelprioritization (LCP) procedure based on the association priorities for adata transmission to a receiving base station.
 13. The method of claim12, wherein the LCP procedure involves: performing a LCP procedure onradio bearers associated with the receiving base station; determiningwhether there is any radio resource left; and performing a LCP procedureon radio bearers not associated with the receiving base station.
 14. Themethod of claim 1, further comprising: cancelling an SR to be sent tothe selected base station upon detecting one or more conditionscomprising: a buffer status report (BSR) being transmitted to theassociated base station, and receiving an uplink grant that allows alldata to be transmitted.
 15. A method comprising: detecting a schedulingrequest (SR) triggered by a user equipment (UE) in a wireless networkwith a plurality of component carriers from multiple base stations,wherein the UE is configured with multiple radio bearers (RBs) that areassociated to one or more logical channel groups (LCGs) and the UE isassociated with multiple cell groups (CGs) in different base stations,and wherein one or more RLC bearer is associated with a base station;transmitting a SR to the base station associated with the RLC bearers;detecting an SR attempt failure event; sending an SR failure indicationto a radio resource control (RRC) layer; and performing an enhancedadjustment based on the SR failure indication.
 16. The method of claim15, wherein the SR attempt failure event is detected when a predefinedSR maximum retry attempts have reached.
 17. The method of claim 15,wherein the enhanced adjustment involves generating an RRC messageindicating a SR failure and sending the RRC message to a Radio AccessNetwork.
 18. The method of claim 15, wherein the enhanced adjustmentinvolves associating the RLC bearer with a different base station.
 19. Auser equipment (UE) comprising: a transceiver that transmits andreceives radio signals from multiple base stations in a wirelessnetwork; a processor coupled to the transceiver and configured to:detect a scheduling request (SR) trigger event; configure a plurality ofcomponent carriers from multiple base stations, wherein the UE isconfigured with multiple radio bearers (RBs) that are associated to oneor more logical channel groups (LCGs), and the UE is associated withmultiple cell groups (CGs) in different base stations; associate eachradio bearer with one or more base stations according to predefinedassociation priorities, wherein each radio bearer associates with one ormore base stations with the same or different priority; and select oneor more base stations to which one or more SRs are sent based on theassociation priorities.
 20. The UE of claim 19, wherein the associationpriorities are configured by the wireless network via a radio resourcecontrol (RRC) configuration.
 21. The UE of claim 19, wherein theassociation priorities are derived based on predefined UEconfigurations, comprising: a base station or a CG that houses a PCellfor CA, a base station configured with femto or pico cells which havethe highest priority, and a base station with cells configured with apredefined carrier frequency.
 22. The UE of claim 19, wherein theassociation priorities are derived from load information received by theUE.
 23. The UE of claim 19, wherein the association priorities arederived from radio measurements.
 24. The UE of claim 19, wherein the setof association priorities is specific to an access channel on which theSR is sent.
 25. The UE of claim 24, wherein dedicated access channelsare given high priorities over contention based channels.
 26. The UE ofclaim 19, the processor is further configured to cancel an SR to be sentto the selected base station upon detecting one or more conditionscomprising: a buffer status report (BSR) being transmitted to anotherbase station, and receiving an uplink grant that allows all data to betransmitted.
 27. The UE of claim 19, the processor is further configuredto: upon detecting a predefined number of SR attempt failures, send anSR failure indication to a radio resource control (RRC) layer andperforms an enhanced adjustment based on the SR failure indication. 28.The UE of claim 27, wherein the enhanced adjustment involves generatingan RRC message indicating a SR failure and sending the RRC message to aRadio Access Network.
 29. The UE of claim 27, wherein the enhancedadjustment involves associating the triggering radio bearer with adifferent base station.